Snails “rode on birds” to remote islands -study

January 25, 2006

LONDON (Reuters) – Land snails, not the quickest of
creatures, managed to travel from Europe to remote islands in
the South Atlantic by hitching rides on birds.

Scientists had assumed that snails living on the Tristan da
Cunha islands midway between South Africa and Brazil were a
different species from those in Europe but researchers in the
Netherlands and Britain have shown they belong to the same
family.

“Land snails, which we normally think of as being rather
slow moving, can actually disperse enormous distances by
hitching rides on birds,” said Richard Preece, of the
University of Cambridge, in England in an interview on
Wednesday.

A genetic analysis of snails from the isolated islands,
which were thought to be unique to them, revealed they belong
to the genus Balea just like their European cousins.

“We have shown that they are indeed exactly the same genus
as Balea,” said Preece, who reported the finding in the journal
Nature.

The arrival of the snails on the islands predates their
discovery by humans. So the scientists believe the European
snails which cannot swim or fly traveled the 9,000 km (5,592
miles) to the Tristan da Cunha islands on birds.

“It must have gotten there, we think, on some sort of
migrating bird,” said Preece, adding it was probably a wader.

The genetic trail suggests the snails dispersed from Europe
to the Azores and the Tristan da Cunha islands and then back
again.

“One of the species on the Azores returned to Europe,”
Preece added. “It seems that having got there in the first
instance a very long time ago, it relatively recently migrated
back to Europe.”